WO2006089382A1

WO2006089382A1 - Electro-acoustic transducer

Info

Publication number: WO2006089382A1
Application number: PCT/BR2005/000145
Authority: WO
Inventors: Antonio Katsushi Fujimoto
Original assignee: Gradiente Eletrônica S.A.
Priority date: 2005-02-23
Filing date: 2005-07-29
Publication date: 2006-08-31
Also published as: BRPI0500605A

Abstract

The present invention refers to an electro-acoustic transducer (10) that includes an arrangement of at least two small thickness, low power and high impedance sound sources (20 - 29), available in a panel (30), where such arrangement must correspond to the relation Pt = ΣPi and lt = li/ΣN, where Pt is the total power of the electro-acoustic transducer in accordance with the present invention, and ΣPi is the sum of the individual power of each sound source (20 - 29) applied in the arrangement; and It is the total impedance of the electro-acoustic transducer in accordance with the present invention, li is the individual impedance of every sound source (20 - 29), and ΣN is the sum of the number of sound sources applied in the arrangement.

Description

"ELECTRO-ACOUSTIC TRANSDUCER"

FIELD OF THE INVENTION

The present invention generally refers to an electro-acoustic transducer. More specifically, the present invention refers to an electro-acoustic transducer of small thickness, which comprises an arrangement of a plurality of sound sources of small thickness, low power and high impedance, being that the result of the power and impedance of such arrangement corresponds to the transducer's total power and impedance.

The subsequent definitions will be used for the following specification:

- Electro-acoustic transducer: device capable of converting an electrical signal into a mechanical vibration for reproduction of an audible sound or not.

- Sound source: adequate means for reproduction of a sound wave.

- Power: is the maximum electric power that can be applied in an electro-acoustic transducer, expressed in Watts (W).

- Impedance: is the resulting measurement obtained from the sum of the dc ohm resistance and the inductance and capacitance of an electro- acoustic transducer to the passage of an electric current, expressed in ohms (Ω).

- Resounding cabinet or acoustic box: a box manufactured in an adequate material (such as wood, thermoplastic, masonry or fiberglass) in which an electro-acoustic transducer is assembled for a determined sound resonance.

- Small thickness: a thickness of about 5 to about 15 mm, particularly from about 7 to about 12 mm, more particularly from about 8 to about 10 mm. Not depending on accessories, frames or finishing boxes. W

- Low power: power value comprised between about 1 and about 10 W, particularly between about 2 and about 8 W, more particularly between about 3 and about 7 W.

- High impedance: impedance value comprised between about 10 and about 100 Ω, particularly between about 20 and about 80 Ω, more particularly between about 30 and about 60 Ω.

BACKGROUND OF THE INVENTION

Electro-acoustic transducers, particularly loudspeakers, are devices that, in a general way, comprise a magnet, a coil and a vibrating membrane of paper pulp or polymeric material, for example. The operating principle of electro-acoustic transducers is well known to those skilled in the art: an electric signal excites a coil that is surrounded by a magnetic field reproduced by a magnet fixed to the membrane, causing the membrane to vibrate at a determined frequency. The membrane, thus, converts the mechanical vibration into a sound wave.

Constructive features, size and proportions of electro-acoustic transducers may vary depending on the type of application for which they are intended, the range of frequency response, and the quality of the reproduced sound. However, regardless the type of application, there is a constant concern with the reduction of the dimensions of the electro-acoustic transducer, in particular its thickness. That is because sound and video equipment technology has been developing for a better efficiency of these speakers to and, at the same time, to occupy the least space possible. Moreover, the market desires to purchase electro-acoustic transducers of small thickness to combine them with plasma or LCD televisions, and also to enable them to be fixed onto a wall, as if they were paintings, for an aesthetic harmony with modern electronic devices, which are increasingly thinner. The great limiting factor for reduction of electro-acoustic transducer thickness is usually the membrane and the magnet. The membrane because it must have a good mechanical resistance to prevent deformation. Usually, the membrane has a cone shaped form with a determined depth for a good sound reproduction. The magnet because its size is closely associated with the power to move the membrane for an adequate power response in commercial applications.

Furthermore, another limiting factor for reduction of electro- acoustic transducer thickness is the need of assembling them in conjunction with a resounding cabinet. Until today, it has not been able to fully eliminate the need of employing the resounding cabinet for a reasonable sound reproduction, specifically the reproduction of low frequencies, in order to not annul the sound wave reproduced by the front part of the membrane with the sound wave reproduced by the rear part of the membrane. In other words, the resounding cabinet has the purpose of allowing low frequencies sound reproduction in a clear and well-defined manner.

The state of the art shows various attempts at constructing an electronic transducer of small thickness.

North-American patents US 3,919,499 and US 4,417,172 reveal an electro-acoustic transducer in which the coils are assembled directly on a plane diaphragm divided into various sectors of different dimensions. A plurality of magnets causes the coil and diaphragm to vibrate at different frequencies.

The North-American patent US 4,385,210 describes an electro- acoustic transducer that uses a plane diaphragm of small thickness that is activated by a plurality of magnets spaced from each other. According to this document, there are two diaphragms, one for reproduction of low frequencies (woofer) and another for reproduction of high frequencies (tweeter). The frequency of the signal for each diaphragm is divided by a crossover. The patent US 4,899,390 shows an electro-acoustic transducer of small thickness that uses a series of coils connected to at least one plane diaphragm, in association with a resounding cabinet for a good sound propagation. The publication WO 91/04643 describes an electro-acoustic transducer equipped with a plane diaphragm in which an electric conductor is assembled in the form of a coil. The coil assembled in the diaphragm is excited by a series of magnets that cause the diaphragm to vibrate at a determined frequency and, as a result, reproduce the sound. The North-American patent US 5,539,835 reveals a plane diaphragm with regions of different densities, being that each region is responsible for the reproduction of a determined frequency.

However, prior art electro-transducers do not eliminate the need of using resounding cabinets for a perfect sound reproduction. That is because all the solutions imply the use of plane diaphragms, some as a single component, which requires the use of a resounding cabinet so that the sound frequency generated by the rear part of the diaphragm does not annul the sound frequency generated by the front part of the diaphragm.

Furthermore, these transducers of the state of the art have a complex structure, in which a plurality of magnets and/or coils is assembled directly on a single diaphragm or diaphragms of different densities or sizes for reproduction of determined frequency ranges.

Moreover, some of the solutions of the state of the art necessarily imply the use of frequency dividers, or crossover, which make the final product more expensive, and are additional devices necessary for the operation of the electro-acoustic transducer.

Therefore, it is an object of the present invention an electro- acoustic transducer of small thickness in which there is no use of a plane diaphragm or a single diaphragm, and that provides a simpler structure in comparison with electro-acoustic transducers of small thickness of the state of the art.

It is another object of the present invention an electro-acoustic transducer that eliminates the need of using a resounding cabinet.

Yet another objective of the present invention is an electro- acoustic transducer that does not require a frequency divider to separate the frequency ranges, or the use of a crossover.

Finally, another objective of the present invention is an electro- acoustic transducer in which its thickness is less than or at least equal to the thickness of prior art electro-acoustic transducers.

DESCRIPTION OF THE INVENTION

The abovementioned objectives, among others, are attained with the present invention, which concerns an electro-acoustic transducer that comprises the assemble of at least two sound sources of small thickness, low power and high impedance in a panel, being that said arrangement matches the relation P_t = IP₁ and l_t = I/ΣN.

According to the present invention, an electro-acoustic transducer is formed by the assemble of at least two sound sources, which can also be electro-acoustic transducers, of small thickness, low power and high impedance. However, a greater number of sound sources can be employed, particularly between 5 and 20 sound sources, and more particularly between 8 and 15 sound sources.

Said arrangement must attend to the relation P_t = ΣPj, where P_t is equal to the total power of the electro-acoustic transducer according to the present invention, and ΣPj is the sum of the individual power of each sound source of small thickness, low power and high impedance. The power is measured in Watts (W). W 2

The power range of each sound source may vary between about 1 and about 10 W, particularly between about 2 and about 8 W, and more particularly between about 3 and about 7 W. Each sound source must however have the same power. The total impedance of the electro-acoustic transducer of the present invention must also attend to the relation l_t = Ij/ΣN, where l_t is the total impedance of the electro-acoustic transducer according to the present invention; Ij is the individual impedance of each sound source of small thickness, low power and high impedance; and ΣN is the sum of the number of sound sources used in the arrangement.

The impedance range of each sound source of small thickness, lower power and high impedance may vary between about 10 and about 100 Ω, particularly between about 20 and about 80 Ω, more particularly between about 30 and about 60 Ω. However, the impedance of each sound source, individually, should be equal.

The sound sources of small thickness, low power and high impedance might be arranged on a surface that may be plane or slightly curved and that defines a panel. The arrangement may vary, such as a parallel arrangement, a circular arrangement, in line, triangular, or any other arrangement deemed necessary. The alignment or arrangement of the sound sources of the electro-acoustic transducer is not relevant to the present invention, although an esthetic distribution would be commercially appreciated.

The sound sources arranged on said panel should be spaced from each other for good reproduction of sounds of low frequency, such as frequencies of less than 200 Hz. The spacing between each sound source as well as the spacing between each sound source and the end of the panel should be between about 5 and about 100 mm, particularly between about 8 and about 50 mm, and more particularly between about 10 and about 25 mm. The material of the panel may also vary according to need. The following materials, for example, may be employed: wood, fiberglass, carbon fiber, polymeric materials, etc. The panel's thickness may also vary according to the need, being that said thickness should not exceed 10 mm. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will explained hereinafter with reference to a particular embodiment, with reference to the attached drawings, incorporated in the present specification by reference. Such drawings are schematic, and their size and proportion may not correspond to reality, since they only aim to didactically illustrate the present invention without imposing any limitations besides those in the attached claims, wherein:

Figure 1 is a frontal schematic view of an embodiment of the electro-acoustic transducer according to the present invention;

Figure 2 is a side schematic view of an embodiment of the electro- acoustic transducer according to the present invention; and

Figure 3 is a scheme of the electrical circuit of an electro-acoustic transducer according to the present invention.

DESCRIPTION OF A PARTICULAR EMBODIMENT With respect to figures 1 and 2, it is schematically illustrated an electro-acoustic transducer according to an embodiment of the present invention.

The electro-acoustic transducer (10) of the present invention, in this particular example, is formed by the association of 10 sound sources (20- 29) mounted in a panel (30). The panel (30) is intended to fix in an appropriate manner the assembly of the plurality of sound sources of small thickness, low power and high impedance. The arrangement illustrated in Figure 1 is of two parallel rows, each one having 5 sound sources, totaling 10 sound sources. According to the embodiment herein described, the sound sources employed (20-29) are electro-acoustic transducers of classic construction, i.e., circular, of slightly conic membrane with coil on the rear part. These transducers (20-29) have low power, e.g. 3 W, high impedance, e.g. 40 Ω, and low thickness, about 8 to about 10 mm. These transducers (20-29) have a good frequency response in a frequency range of about 50 to about 25,000 Hz, more particularly of about 100 to about 15,000 Hz.

The electro-acoustic transducer (10) according to the present invention follows the relation: P_t = ΣPj, wherein P_t is the total power of the electro-acoustic transducer (10), and ΣPj is the sum of the individual potencies of each source of small thickness, low power and high impedance, the power being measured in Watts (W).

According to this embodiment, each sound source (20-29) has a power of 3 W, the total power of transducer (10) being of 30 W, i.e., a power value commercially acceptable for home and automotive applications.

The electro-acoustic transducer (10) according to the present invention also follows the relation l_t = I|/ΣN, wherein l_t is the total impedance of the electro-acoustic transducer (10), Ij is the individual impedance of each sound source (20-29), and ΣN is the sum of the number of sound sources (20- 29) employed in the arrangement, impedance being measured in ohms (Ω).

According to this embodiment, each sound source (20-29) has an impedance of 40 Ω, and the total impedance of the electro-acoustic transducer

(10) is of 4 Ω, a perfectly acceptable value for home and automotive applications, which generally use electro-acoustic transducers of 4 to 8 Ω, and in particular cases of 2 to 16 Ω.

Figure 3 schematically illustrates the electric connection of the sound sources (20-29) in parallel, in which the relations P_t = ΣPi and l_t = I/ΣN are attained. Back to figures 1 and 2, it is represented that a panel (30) is employed to arrange the sound sources (20-29). The panel (30) may be embodied with several appropriate materials, such as wood, glass fiber, carbon fiber, polymeric materials, etc. According to this embodiment, it is employed a polystyrene panel, and the sound sources are fixed therein by appropriate means, such as an adhesive. The panel (30) must have an appropriate thickness for fixing the sound sources and to maintain a low vibration of the set and the small thickness transducer (10).

The space (b) between each sound source, as well as the space (c) between a sound source (20-29) and the panel end (30) must be appropriate for the reproduction of low frequencies, particularly frequencies under about 200 Hz. According to this embodiment, the space (b) between each sound source and the space (c) between each sound source and the panel end (30) is of about 10 mm. The use of the panel (30) completely eliminates the need of using resounding cabinets for electro-acoustic transducers, due to the fact that it impedes the frequencies generated by the front part (40) of the sound sources (20 to 29) to be cancelled by the frequencies generated by the rear part (50) of the sound sources (20 to 29). The embodiment described herein does not reveal a finishing framework for the transducer (10) of the present invention. Obviously, in accordance with the need and taste, a finishing box can be applied on the transducer (10) for aesthetics to the environment where it will be applied. The finishing box is not relevant to the scope of the present invention. Therefore, the present invention overcomes the problems found in the small thickness electro-acoustic transducers of prior art, due to the elimination of resounding cabinets, for presenting a less complex construction in comparison to the thin transducers of the state of the art, and also for eliminating the need of using frequency separators, or crossover.

It must be understood that although the present invention has been described in relation to a particular embodiment, those skilled in the art may develop a wide variation of structural and operational details, as well as expand the electro-acoustic transducer of the present invention for other applications without, however, deviating from the principles of the present invention. Therefore, the attached claims must be interpreted as covering all equivalents that are within the scope and character of the invention.

Claims

1. Electro-acoustic transducer, characterized by comprising an arrangement in a panel of at least two sound sources of small thickness, low power and high-impedance, wherein said arrangement matches the relation P_t = ΣPj and I_t = I/ΣN, where P_t is the total power of the electro-acoustic transducer, ΣPj is the sum of the individual power of each said sound source employed, l_t is the total impedance of the electro-acoustic transducer, h is the individual impedance of the each said sound source employed, and ΣN is the sum of the number of sound sources employed.

2. The Electro-acoustic transducer according to claim 1 , characterized in that the thickness of each sound source is between about 5 and about 15 mm, particularly between about 7 and about 12 mm, more particularly between about 8 and about 10 mm.

3. The Electro-acoustic transducer according to claim 1 , characterized in that the individual power (Pj) of each sound source is between about 1 and about 10 W, particularly between about 2 and about 8 W, more particularly between about 3 and about 7 W.

4. The Electro-acoustic transducer according to claim 1 , characterized in that the impedance (Ij) of each sound source is between about 10 and about 100 Ω, particularly between about 20 and about 80 Ω, more particularly between about 30 and abut 60 Ω.

5. The Electro-acoustic transducer according to claim 1 , characterized in that said sound sources are electro-acoustic transducers.

6. The Electro-acoustic transducer according to claim 1 , characterized in that said sound sources are connected in parallel.

7. The Electro-acoustic transducer according to claim 1 , characterized in that the number of sound sources employed is between 5 and 20 sound sources, particularly between 8 and 15 sound sources.

8. The Electro-acoustic transducer according to claim 1 , characterized in that said sound sources have a response to frequencies from about 50 to about 25.000 Hz, particularly from about 100 to about 15.000 Hz.

9. The Electro-acoustic transducer according to claim 1 , characterized in that said panel (30) has a thickness (e) between about 1 mm and about 10 mm.

10. The Electro-acoustic transducer according to claim 1 , characterized in that said sound sources are spaced between themselves (b) at a distance of about 5 and about 100 mm, particularly of about 8 and about 50 mm, more particularly of 10 and 25 mm.

11. The Electro-acoustic transducer according to claim 1 , characterized in that the spacing (c) between said sound sources and the edge of the panel is between about 5 and about 100 mm, particularly about 8 and about 50 mm, more particularly about 10 and 25 mm.

12. The Electro-acoustic transducer according to claim 1 , characterized in that said sound sources are arranged in equal number, one on side of the other in two rows.

13. Use of at least two small thickness, low-power and high impedance sound sources for the construction of an electro-acoustic transducer (10).